Ryan Graves was the company's first employee and first CEO.

REUTERS/Beck Diefenbach

When Graves responded "heres a tip. email me:)" to a tweet about a startup job, there was no way of knowing Uber would become the $62 billion company it is today.

Graves joined and became its first CEO and general manager from February 2010 until December 2010. At that point, Graves was "super pumped" that Kalanick (who was "frickin' pumped") would take over the role.

Since then Graves has been in charge of leading Uber's international expansion and growth as SVP and head of global operations. He's also on Uber's board.

Austin Geidt is in charge of expanding Uber everywhere.

Austin Geidt/Twitter

Joining the ride-hailing startup after battling a drug addiction, Geidt was the fourth hire at Uber and has been with the company ever since.

"I'm so proud of the work my team has done at Uber and the work I've done at Uber. But it's not the proudest thing I've done, right? I'm more proud of being sober," she said at a Fortune conference. "I just have perspective."

As head of global expansion, she's taken Uber from one city to more than 100 and plots on a map where Uber is going next.

If that wasn't enough of a job, she also oversees the PRO team, Uber's equivalent to business ops, that's in charge of streamlining the company. One of her special projects is Uber's 1 Million Women initiative to sign up 1 million women to the platform by 2020.

Thuan Pham makes sure the Uber app stays up and running.

Uber

As Uber's chief technology officer, Thuan Pham has been leading Uber's technology staff from a team of 40 to more than 1,200 engineers.

It hasn't been without its challenges — a report from The Information said Pham was "deathly afraid" of the consumer app going down as it grows — but Pham is universally described as the inspirational leader Uber's technology team needs.

Joe Sullivan is an ex-Facebook security guru in charge of keeping Uber riders and drivers safe.

He's also in charge of making sure the data Uber collects stays secure, especially after a few high-profile mishaps, like a recent breach in which more than 50,000 drivers' personal information was put at risk.

Sullivan has the background to do it. While his career started out as a lawyer fighting cybercrime, Sullivan switched to working within tech companies, starting with eBay. The bulk of his career was spent at Facebook, where he spent eight years shepherding the then young company. His hire last April was a big poach for Uber, and Sullivan's been luring more ex-Facebookers since.

Jeff Holden is in charge of building the future of transportation.

Jeff Holden

Whether it's creating UberPOOL or dreaming up a future of autonomous cars, Jeff Holden is in charge of building it as chief product officer. One of his biggest projects has been the Carnegie Mellon deal and subsequent research operations into building autonomous cars.

Holden joined Uber in 2014 from Groupon, but that's likely not the experience Kalanick hired him for. Before that, Holden was a key player at Amazon and as described as the "mercury" planet orbiting closest to Bezos' Sun, according to Brad Stone's book, "The Everything Store."

Emil Michael wants businesses to work with Uber.

Michael's job was on the line in November 2014 after he made threatening remarks about digging up dirt on a journalist. Michael, the SVP of business development, has stayed with the ride-hailing company since as its lead in partnerships.

Lately, much of Michael's work has been to grow Uber China and try to forge new ground in China by striking local partnerships, including one with Baidu.

Brian McClendon, a former Googler, is bringing autonomous cars to Uber.

Justin Sullivan/Getty Images

At Google, Brian McClendon was known as the maps guy having been a VP and early leader in the creation of Google Maps and Google Earth.

But after a decade at the search giant, McClendon joined Uber to take it into the future. McClendon is now the vice president of Uber's Advanced Technologies Center, where he oversees the research into autonomous cars, mapping, and safety.

Jason Droege is in charge of transforming Uber's business from just cars to everything.

Twitter

Droege is an exec who gets a little bit of room to experiment. As head of UberEverything, Droege leads Uber's delivery efforts like UberEATS and UberRush — two experiments that have gone on to become big business pursuits.

Droege and his team are in charge of choosing which cities would be great for delivery (Barcelona got UberEATS before San Francisco) and terminating the programs that don't work.

Amit Jain faces fierce competition expanding Uber into India.

LinkedIn

With Ola as a fierce competitor, Uber tapped Jain to run its entire India unit in June 2015. The former president of Rent.Com moved to New Dehli from Silicon Valley and is now in charge of everything Uber does in the country, an area that Kalanick has promised to spend $1 billion to gain market share.

Tim Collins wants to keep Uber's customers safe and happy.

It's not an easy job, but Collins is in charge of leading Uber's customer support and safety operations around the globe.

After spending years leading Amazon's Europe operations, Collins joined Uber to become its VP of global community operations in January 2015. Upon his hiring, one of Collins' first tasks was to establish Safety Incident Response teams that could roll out at a moment's notice in case of a "safety event."

Allen Penn is growing Uber's hotly contested operations in Asia.

Penn joined Uber in 2011, just as Chicago was getting off the ground and Uber was only in six cities. Now Penn has spent the last two years based in Hong Kong and leading all of Asia's operations.

It's a tough job that includes overseeing both India and China, two markets that Uber has promised to invest $1 billion each to overcome the local rivals.

Uber has also faced backlash from other markets like South Korea, after the country threatened to arrest Kalanick for operating without the proper license. From his base in Hong Kong, Penn oversees it all as head of Asia operations.

Salle Yoo has tackled new legal ground (and all of the lawsuits).

Twitter

Uber is no stranger to being hit with legal action, and it's been Yoo's responsibility as general counsel to combat it. Since joining Uber more than three years ago, Yoo has grown Uber's legal team from one to 120 employees.

One thing that Yoo is also passionate about: equal pay. She's known for asking HR to rerun offer letters if she doesn't think it represents equal pay, and tries to hire female leaders early on her teams.

Renee Atwood powers Uber's employees.

YouTube

When Renee Atwood joined Uber it only had 605 employees. Now the global head of people is in charge of nearly 5,000. Atwood leads Uber when it comes to all things people, including recruiting and HR.

Recently Atwood was behind another of Uber's big moves: its new headquarters in Oakland, California.

Rachel Whetstone controls Uber's message.

Uber poached Rachel Whetstone from a similar role at Google to become its new SVP of policy and communications, and her goal is to give Uber a bit of a softer side. It's a delicate balance, and Whetstone has been staffing up on more political talent to maintain.

David Plouffe must convince politicians and the public Uber is a good thing.

AP/ Ross D. Franklin

Described as "a leader for the Uber campaign," former Barack Obama campaign manager David Plouffe joined Uber to head up its public policy team. A few months later, Rachel Whetstone assumed the role and Plouffe was moved to chief adviser (and board member of the company).

However, that doesn't mean his role has diminished. Instead, Plouffe is one of the few highly visible members of Uber's upper echelon, hitting the so-called campaign trail in public appearances and meetings with government officials.

Uber is the most valuable private tech company in the world, and Gautam Gupta is in charge of running its finances.

LinkedIn

Uber has been missing a CFO for almost a year now, but it still has someone behind the scenes looking over the books.

After Brent Callinicos left in March, Gautam, his "right hand on strategic finance," became the head of finance for the ride-hailing company.

Ed Baker has one goal: growth.

About.Me

If Uber is going to make transportation as reliable as running water, it's going to need to grow to do it. Baker was leading international growth at Facebook before he joined Uber in 2013 to become its VP of growth.

In Baker's charge are the engineers, product managers, and marketing teams that are trying to attract both new riders and drivers to the platform. Uber's growth team is known to value speed and iteration to support its fast-moving marketplace.

Travis Vanderzanden defected from Lyft to help grow Uber.

LinkedIn

In what certainly lit the flames in the rivalry between Lyft and Uber, former Lyft COO Vanderzanden joined Uber to become its VP of supply growth.

Vanderzanden works closely with Baker on bolstering the company's growth, especially in the international markets.

Jo Bertram runs Uber for the Brits and the Irish and for the Nordic countries.

Leading the fight for Uber in the UK, Ireland, and Nordic countries, Bertram is no stranger to conflict. The UK has seen some of the biggest protests against the ride-hailing company, and Bertram herself has been a target of Twitter trolls in the process.

As regional general manager for the UK, Ireland, and Nordic countries and the public face for Uber in those countries, Bertram is in charge of all the operations, policy, and new product launches in countries still addicted to using black cabs.

Rachel Holt is in charge of Uber on both coasts.

Uber

As the regional general manager for both the East and West Coasts of the US, Rachel Holt oversees some of Uber's biggest markets, including Washington, D.C., where she is based.

The term "general manager" doesn't capture how high-ranking of a role it is within Uber's internal structure, and Holt enjoys a close relationship with Kalanick, who sent her an Uber-branded onesie for the birth of her child.

“Uber is a place where the best ideas win. That is because of Travis,” she told Newsweek in an interview. “And it makes it one of the most rewarding places you can work. If you have a good idea, and you email him with that idea, you’ll be the one running that project that week. That’s pretty special, and pretty unique, for the CEO of a company as big as Uber.”

Andrew Macdonald runs Uber in the central US and all of Latin America.

Uber

"Mac" as he's known for short has been with Uber since the early days in Chicago. Since then, Macdonald has risen through the ranks, and is now the regional manager of the central US and Uber's Latin American markets.

Before Uber, Macdonald had a different kind of transportation job:

"My summers in University were spent building pick-up trucks at a General Motors factory. 438 trucks per 8-hour shift. There was about 20-30 seconds of downtime in between each truck rolling by, in which I’d quickly read a sentence or two from whatever book I had going. I used to get through a few books a week," he said in an Uber bio.

Pierre-Dimitri Gore-Coty is facing a trial in France.

Gore-Coty is an executive to stand by his company. Based in the Netherland, Gore-Coty is the head of operations for EMEA and former regional general manager for Western Europe.

Gore-Coty made international headlines when he and Uber's France GM were held by French police and charged with deceptive business strategies and illegally operating a taxi company. It was last reported in October that the trial had been delayed until at least February.

France has been a hotly contested market for the company, and it's been in Gore-Coty's charge to transform it into a successful one.